Abstract: :
Purpose: When a low spatial frequency sinusoidal grating undergoescounterphase flicker at a high temporal frequency, the spatialfrequency of the grating is perceived as doubled. FrequencyDoubling Technology 2 (FDT2) is a promising new modality forthe evaluation of patients with neuro-ophthalmic disorders.The FDT2 24-2 program has 55 test points as compared to 17 forthe previous FDT C-20 program. The purpose of this study wasto compare the FDT2 perimeter with the Humphrey (HFA II) perimeterfor optic nerve and chiasmal neuro-ophthalmic disorders.Methods:Four readers compared correlation between the FDT2 24-2 andHFA II SITA Standard 24-2 test patterns using 126 abnormal visualfields. Our analysis included patients with optic nerve andchiasmal neuro-ophthalmic disorders. The readers assigned separatecorrelations (Good, Fair, or Poor) to each eye using preliminaryTotal and Pattern Deviation probability plots for the FDT2 andstandard Total and Pattern Deviation probability plots for theHFA II. The readers also ranked perimeters by the depth andextent of visual field loss (Equivalent, FDT2, or Humphrey).Results: For the Total Deviation probability plots, 66/126(52%) had Good correlation, 35/126 (28%) had Fair correlation,and 25/126 (20%) had Poor correlation. For the Pattern Deviationprobability plots, 44/126 (35%) had Good correlation, 47/126(37%) had Fair correlation, and 35/126 (28%) had Poor correlation.The extent of the defect as seen on Total Deviation probabilityplots was equal in 58/126 (46%) of cases, more extensive withFDT2 in 36/126 (29%), and more extensive with HFA II in 32/126(25%). The extent of the defect as seen on Pattern Deviationprobability plots was equal in 38/126 (30%) of cases, more extensivewith FDT2 in 47/126 (37%), and more extensive with HFA II in41/126 (33%).Conclusions: The new FDT2 24-2 testing strategyprovides a screening and quantitative visual field testing parameterfor optic nerve and chiasmal neuro-ophthalmic disorders thatcorrelates reasonably well with the HFA II SITA Standard 24-2program. However, there are some clear differences in regardto correlation, extent, and depth of the defect. Further evaluationwill be necessary to evaluate the differences between the programsfor patients with optic nerve and chiasmal disorders.